Fatigue Alters Shock Attenuation during Landings of Sidestep Cutting

Abstract

PURPOSE: Landings in fatigue condition are considered to be one of the factors to cause non-contact anterior cruciate ligament injury. It is known that fatigue alters lower extremity landing strategies and decreases the ability to attenuate shock during landing. However, lower extremity kinematics and shock attenuation during landings of sidestep cutting movement in fatigue condition has not been clarified. The purpose of this study is to reveal characteristic of lower extremity kinematics and shock attenuation during landings of sidestep cutting in fatigue condition. METHODS: Ten healthy female (age = 21.2±2.3 years old, height = 161.5±3.5 cm, weight = 53.9±8.5 kg) volunteered to participate in this experiment. All of them gave written informed consent before this experiment. They performed sidestep cutting movement before and after completing the fatigue protocol. The fatigue protocol was performed by using a bike ergometer. Lower kinematics and kinetics data were obtained from the three-dimensional motion analysis system with eight cameras (Vicon MX, Vicon Motion Systems, Oxford, UK) and three force plates (MSA-6, AMTI, Mass., USA). Maximum knee flexion angle, angular velocity and minimum angular acceleration were analyzed from initial contact to toe off during landings of sidestep cutting movement. Paired T test was used to identify differences of lower extremity kinematics between before and after completing fatigue protocol. RESULTS: Maximum knee flexion angle, angular velocity and times from initial contact to peak knee flexion angle had no differences between before and after completing the fatigue protocol. Minimum knee flexion acceleration increased significantly after completing the fatigue protocol (-146.9 vs. -165.7 rad/s2, P<0.05). CONCLUSIONS: Sidestep cutting movement in fatigue condition decelerated by increasing knee flexion angle in a short time. Maximum knee flexion angle and times from initial contact to peak knee flexion angle during landings of sidestep cutting movement were not altered. Our study indicates that fatigue decreased the ability to attenuate shock by decreasing minimum angular acceleration of knee flexion during landings of sidestep cutting movement.